1. Field of the Invention
This invention relates to an improvement in pneumatic tires comprising a pair of bead portions each containing at least one bead core therein and a carcass of at least one rubberized ply extending between the bead portions and containing organic fiber cords therein, and having a load applied to one bead core per unit length of not less than 6.0 kg/cm.
2. Description of the Prior Art
In the conventional pneumatic tire comprising a carcass of at least one organic fiber cord ply between a pair of bead portions each containing a bead core therein and having a load applied to the bead core of more than 6.0 kg/cm, ply separation between the carcass ply and the bead core is produced at the bead portion and finally the cords of the carcass ply are frequently broken about the bead core. Therefore, there have usually been proposed countermeasures for preventing the breaking of the cords of the carcass ply be reducing the load, for example, the enlarging of rim diameter in the tire, the increasing of bead core number and the like. However, these countermeasures are not favorable in view of tire productivity and resource-saving.
Furthermore, tires having a load applied to a pair of bead cores of more than 6.0 kg/cm have been sold in market by some tire manufactures, but they are not yet sufficient in the durability after the retreading.